This application relates to a retention feature for retaining a planet shaft against rotation in a planetary gear system.
Planetary gear systems are well known, and have been utilized to provide a gear change between an input and an output. A sun gear rotates about a central axis, and a ring gear rotates outwardly of the sun gear. A plurality of planet gears are positioned to transmit rotation between the sun and ring gears.
In one known type of planetary gear system, the planet gears are mounted on stationary shafts positioned inwardly of the gears. The planet shaft provides an inner race for bearings which support the planet gears.
One application of a planetary gear system is in an air turbine starter system. In an air turbine starter system, air is delivered across a turbine rotor to drive the rotor. The rotor drives a sun gear, which drives a ring gear through planet gears. The ring gear in turn drives a starter shaft for a gas turbine engine.
In such applications, a good deal of force is transmitted to the planet shafts, which should remain stationary within a fixed housing. In the prior art, the planet shaft received a set screw which extends radially inwardly at an axially intermediate location. The set screw extends generally directly radially inwardly relative to a rotational axis of the associated planet gear, or a central axis of the shaft.